Re: [TowerTalk] Balun Overheating?

[Grant Saviers <grants2@pacbell.net>]

I melted the commercial "HD QRO" bead type choke off my GOTA G5RV 
feedline junction and since then only use the FT-240-31 cores stacked 3 
or 4 at QRO with TFE coax (RG142 double silver) turns or the "big clamps 
ons" type 31 at up to 500w with RG8X, very convenient.  Why use beads 
when inductance is proportional to turns squared?  A much better use of 
ferrite is a larger core with the appropriate turns per K9YC or G3TXQ's 
data.
Never again G5RV's, fan dipoles rule!

Grant KZ1W


On 4/20/2014 9:24 PM, Roger (K8RI) on TT wrote:
> On 4/20/2014 10:26 PM, Jim Lux wrote:
> > On 4/20/14, 6:34 PM, Tom Hellem wrote:
> > > Fellow TTers:
> > >
> > > I built a balun for my triband yagi consisting of 50 type 73 ferrite 
> > > beads
> > > slipped over a piece of RG 303
> > > coax, enclosed inside of a piece of 1-1/2" pvc. Had one of the wires 
> > > break
> > > inside and I surmised it must have
> > > been a result of wind-caused vibration, etc. So after I repaired the 
> > > broken
> > > connection, I squirted some of that
> > > canned foam insulation (the kind that is sold for foaming around 
> > > windows &
> > > doors, etc.)into the pvc enclosure,
> > >   encasing the entire piece of coax & ferrite beads in the stuff 
> > > thereby
> > > preventing any vibration , etc in the future.
> > > Upon further thought I am wondering now did I invite the balun to 
> > > overheat,
> > > especially while running high power,
> > > as any heat generated has no way to escape.
> > > Does anyone have an opinion one way or 'tother?
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